An amendment can be in the form of a change in the category of a claim, possibly combined with a change in the technical features of the invention. Firstly it must be clear that this amendment is necessitated by grounds of opposition (see IV, 5.3). If that is not the case a change of category should be refused.

Even if this condition is fulfilled, the Opposition Division should exercise great caution in allowing a change of claim category, because the protection as conferred by the claims may be extended (Art. 123(3)). The change of category requested could involve a change from:

If a patent is so amended that a claim to a product (a physical entity) is replaced by a claim to the use of this product, the degree of protection is not extended, provided that the use claim in reality defines the use of a particular physical entity to achieve an effect and does not define such a use to produce a product (G 2/88, OJ 4/1990, 93);

If a patent is so amended that a claim to a product is replaced by a claim to a method for producing the product, this change of category is allowable, provided that the method now claimed only results in the product previously claimed. As it is a fundamental principle of European patent law that the protection conferred by a product claim covers all methods for production of the product, the limitation to one of these methods cannot extend the protection conferred originally (see T 5/90 and T 54/90, neither published in OJ);

If a patent is so amended that a claim to a method of operating a device is replaced by a claim directed to the device itself, this change of category is allowable, provided that the original claim contains the claimed features of the device exhaustively, whether in structural or functional terms (see T 378/86, OJ 10/1988, 386, and T 426/89, OJ 4/1992, 172).

If, however, the device as now claimed is for its features no longer dependent on the circumstances of its operation whereas it depended on them under the terms of the prior method claim, then such a change of category should not be allowed (T 82/93, OJ 5/1996, 274);

By contrast, the change in claim category from a method in which an apparatus is used to the apparatus itself is not allowable (T 86/90, not published in OJ).

The change from a process for the preparation of a product to the use of the product for a purpose other than previously described is also not allowable (T 98/85 and T 194/85, both not published in OJ).

On the other hand, the change in a claim from a method in which a certain product is used to a claim to the use of that product in performing that same method is allowable (see T 332/94, not published in OJ).